Battery pack

ABSTRACT

An object of the present invention is to secure a space in a battery case to house battery cells or minimum gaps to allow swelling of battery cells, so that the battery cells can be held in the battery case without play. 
     A battery pack  1  connects in series and house a plurality of square pole-like battery cells  3  in a battery case  3 , the plurality of battery cells each having a battery lid  32  positioned at the front side thereof, wherein a negative pole side tab  37  that is connected to a battery can bottom  35  of a battery cell and extends to the battery lid side, an intermediate connection tab  36  connecting a positive side pole of the battery cell to a battery can bottom of adjacent another battery cell and a positive pole side tab  34  connected to a positive pole terminal part of said another battery cell are provided, and a cell side insulating sheet  50  is provided between the respective negative pole side tab, intermediate connection tab and the sides of respective battery cans  31 , and a projecting tab for pressing side edge parts  3 E extending in the front and back direction of the respective battery cells, upper corner ribs  13 , small ribs  21  and lower corner ribs  22  (side edge pressing part) are respectively provided on the inner face of the upper side case and on the inner face of the lower side case.

TECHNICAL FIELD

The present invention relates to a battery pack housing a plurality ofsquare pole-like battery cells in a battery case, and particularly tomaintaining the stable state of housing the battery cells in the batterycase.

BACKGROUND ART

A battery pack is used with various kinds of electronic appliances as abattery that is capable of being charged, and such battery pack housesone or a plurality of battery cells in a battery case.

There are some battery cells that are of a flat square pole in shape,and it is efficient in terms of space for these battery cells to behoused in a square pole-like battery case that is one size larger thanthe battery cell.

In addition, the battery pack is provided with a negative pole side tabcreeping over the side of a battery can from the battery can bottom tothe battery can lid side in order to provide a battery terminal at oneend of the battery pack or in a region in the direction of one endthereof.

Further, in the case where a plurality of battery cells are connected inseries, an intermediate connection tab is provided for connecting thebattery can bottom with a positive pole terminal part of adjacentanother battery cell, and the intermediate connection tab is provided tocreep over the side of the battery can as does the above-mentionednegative pole side tab.

Meanwhile, when these negative pole side tab and intermediate connectiontab are disposed creeping over the side of the battery can, there isinterposed an insulation sheet in-between.

In addition, there are provided some battery packs in which theabove-mentioned negative pole side tab and the intermediate connectiontab are respectively divided in two, and PTC (positive temperaturecoefficient) is interposed between these divided tab piece and tab pieceso as to break supply of electric power when the temperature of thebattery cell becomes high.

Further, with the square pole-like battery cell, the central portion ofa rectangle tends to bulge out at a time of the battery cell beingcharged.

Because of the above-mentioned fact, the battery case needs to be formedto be one or two size as large as the outer shape of the battery cell.

However, in the case where the battery case is formed larger than thebattery cell, there occurs a problem in which the battery cell becomewobbly in the inside thereof.

When the battery cell becomes wobbly in the battery case, theabove-mentioned negative pole side tab and the positive pole side tabthat are connected to the battery terminal repeat deformation that leadsto a trouble in which these tabs are damaged as the battery terminal isconventionally fixed to the battery case.

In addition, when the battery cell become wobbly, the above-mentionednegative pole side tab and the intermediate connection tab move andshift from the insulation sheet, resultantly leading to a trouble suchas a short circuit of power.

DISCLOSURE OF THE INVENTION

An object of a battery pack of the present invention is to secure aspace in a battery case for housing battery cells as well as gaps toallow minimum swelling of a negative pole tab and an intermediateconnection tab so as to prevent the housed battery from becoming wobbly.

The battery pack of the present invention is a battery pack for housingin a battery case a plurality of square pole-like battery cells byconnecting them in series; the battery case being comprised of an uppercase and a lower case, respectively in box shape, in such a fashion thatthey are combined with each other; the plurality of battery cells, eachhaving a battery lid positioned on the front side, being housed side byside in the left and right direction in the above-mentioned batterycase, comprising a negative pole side tab that is connected to thebattery can bottom of a battery cell and extends to the battery lidside, an intermediate connection tab that connects a positive poleterminal part of the negative pole cell with the battery can bottom ofadjacent another battery cell and a positive pole side tab connected toa positive pole terminal part of said another battery cell, with theabovementioned negative pole side tab and intermediate connection tabbeing disposed both creeping over the sides of the respective batterycells and being divided into two of a can bottom side tab and a batterylid side tab, respectively. And PTC (positive temperature coefficient)is interposed between these can bottom side tab and battery lid side taband a cell side insulating sheet is provided between the respectivenegative side tabs, intermediate connection tabs and the sides of therespective battery cans, with side edge pressing parts for pressing sideedge portions extending in the front and back direction of therespective battery cells being respectively provided on the inner faceof the upper case and on the inner face of the lower case when the uppercase and lower case are combined with each other.

Therefore, according to a battery pack of the present invention, sinceside edge pressing parts for pressing side edge portions extending inthe front and left direction of battery cells are provided in a batterycase, it is possible to hold the battery cells in the way that thebattery cells do not become wobbly when they are housed in the batterycase, and at the same time, since a predetermined gaps are formedbetween the central portions of the battery cells housed in the batterycase and a separator so that when the central portions of the uppersurface and under surface of the battery case bulge out due to swellingof the battery cells at a time of the battery pack being charged, theabove-mentioned gaps can absorb the amount of bulging, it is possible toprevent the whole of the battery case from swelling and deforming.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the whole of a battery pack, showing anembodiment applied to the battery pack with four battery cells;

FIG. 2 is a perspective view of a battery case being exploded up anddown;

FIG. 3 is a perspective view seen from the backward direction of a statein which the battery case is removed;

FIG. 4 is a perspective view shown by exploding two upper and lowerpairs of the four battery cells and a separator in the upper and lowerdirection;

FIG. 5 is a perspective view of the four battery cells and a substrateexploded in the front and back direction;

FIG. 6 is a perspective view of exploded two left and right batterycells and respective tabs;

FIG. 7 is a bottom view of an upper side case;

FIG. 8 is a plan view of a lower side case;

FIG. 9 is a perspective view of the separator obliquely seen from theupper front direction;

FIG. 10 is a perspective view of the separator seen obliquely from thelower front direction;

FIG. 11 is a cross-sectional diagram along an XI—XI line of FIG. 9;

FIG. 12 is a cross-sectional diagram along an XII—XII line of FIG. 9;

FIG. 13 is a perspective diagram, after cutting off the battery pack atthe approximately central portion thereof, showing respective portionsby exploding them up and down;

FIG. 14 is a cross-sectional diagram along an XIV—XIV line of FIG. 1,showing an expanded portion thereof;

FIG. 15 is a cross-sectional diagram along an XV—XV line of FIG. 1,showing an expanded portion thereof;

FIG. 16 is an enlarged cross-sectional view of the battery pack;

FIG. 17 is an enlarged longitudinal view of the battery pack being cutoff at a position including a battery terminal in the longitudinaldirection, showing the battery cells and separator that are not cut off;

FIG. 18 is an enlarged longitudinal cross-section view of the batterypack being cut off at a position including the battery pack in thelongitudinal direction;

FIG. 19 is a cross-sectional diagram by enlarging an opening peripheraledge of the upper side case;

FIG. 20 is a cross-sectional diagram by enlarging an opening peripheraledge of the lower side case;

FIG. 21 is a cross-sectional diagram showing an enlarged state of theopening peripheral edge of the upper side case and the openingperipheral edge of the lower side case being joined with each other;

FIG. 22 is a cross-sectional diagram showing a state in which ultrasonicwelding is applied to the state of FIG. 1;

FIG. 23 is a plan view schematically showing a state of the battery packbeing placed on a receiving platform of an ultrasonic welding device;and

FIG. 24 is a side view partially showing a cross-sectional state of thebattery pack being placed on the receiving platform of the ultrasonicwelding device.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a battery pack 1 of the present invention will be explainedin detail according to embodiments shown in the following drawings.

The battery pack 1 comprises a square pole-like battery case 2, fourbattery cells 3, 3 . . . , a separator 4 to separate the battery cells3, 3 that are disposed upward and downward out of the battery cells 3, 3. . . , a substrate 6 on which an IC chip 5 is mounted to compute andstore the remaining amount of the battery pack 1 and a battery terminal7 that is exposed from one end surface (front end surface) in thelongitudinal direction of the battery case 2 attached onto the substrate6 (refer to FIG. 2).

By the way, the U direction, the D direction, the L direction, the Rdirection, the F direction, the B direction that are indicated by arrowmarks in respective drawings denote the upward direction, the downwarddirection, the left direction, the right direction, the front directionand the back direction, respectively. In addition, the above-mentioneddirections indicated in this specification are for convenience' sake andare subject to being changed depending on the circumstances in which thebattery pack 1 is used.

The four battery cells 3, 3 . . . are provided in a way that they aresuperposed one on top of another in the up and down direction, and theleft and right direction, which will be described in detail later on.Two of a battery cell 3 r (┌r┘ denotes the right side. Same as above.)and a battery cell 3 l (┌l┘ denotes the left side. Same as above.) arecombined with each other with a double-faced adhesive sheet material 8serving as an insulating member. These cells are connected with eachother in series, which will be described later on, and further, two ofupper side left and right battery cells 3 ur, 3 ul (┌u┘ denotes theupper side. Same as above) and two of lower side left and right batterycells 3 dr, 3 dl (┌d┘ denotes the lower side. Same as above) areconnected in parallel by a circuit pattern (not shown) formed on thesubstrate 6.

The battery case 2 has an upper side case 10 and a lower side case 20,both of which are shaped like a box, and is constituted such that theupper side case 10 and the lower side case 20 are combined with eachother with respective openings thereof made to join with each other(refer to FIG. 2).

The inside dimensions in the left and right direction of the upper sidecase 10 and the lower side case 20 are approximately equivalent to orslightly greater than the left and right width of two of the batterycells 3 ur, 3 ul that are disposed in the left and right direction, andthe inside height of the upper side case 10 is formed greater than theheight dimension of one battery cell 3 with the inside height of thelower side case 20 formed smaller than the height dimension of onebattery cell 3. When the upper side and lower side cases are combined asthe battery case 2, the height of the inside space is formedapproximately equivalent to or slightly greater than the height of twoof the battery cells 3 u, 3 d that are superposed one on top of anotherthrough the separator 4 (refer to FIG. 13).

In the central portion of the upper side case 10, there are formed astepped difference part 11 slightly long in the front and back directionwith the front face side thereof being formed concave and the inner faceside formed convex, and a projecting part 12 approximately on thecentral portion of the inner face side of the stepped difference. Theprojecting part 12 is formed at positions corresponding to upper sideadjacent side edge parts 3E, 3E of two of the battery cells 3 ur, 3 ulthat are provided upper side left and right, which will be describedlater on, so as to press these upper side edge parts 3E, 3E from theupper direction (refer to FIG. 13).

At upper corner portions on the left and right inner face sides of theupper side case 10, there are formed small ribs (hereinafter, to bereferred to as ┌upper corner rib┘) 13, 13, . . . (refer to FIG. 7), andthe upper corner ribs 13, 13, . . . press, from the upper direction, theupper side side edge parts 3E, 3E of the upper side battery cells 3 ur,3 ul housed in the battery case 2 (refer to FIG. 13).

In the central portions of the left and right portions of the lowerinner face of the lower side case 20, there are provided small ribs 21,21 . . . extending in the left and right direction and at appropriateintervals in the front and back direction (refer to FIG. 8), and thesmall ribs 21, 21 . . . are provided at positions corresponding to lowerside adjacent side edge parts 3E, 3E of two of the battery cells 3 dr, 3dl disposed in the lower side left and right direction, which will bedescribed later on, so as to press from the lower direction the lowerside side edge parts 3E, 3E housed in the battery case 2 (refer to FIG.13).

At lower corner portions on the left and right inner face sides of thelower side case 20, there are formed small ribs (hereinafter, to bereferred to as ┌lower corner rib┘) 22, 22, . . . (refer to FIG. 8), andthe lower corner ribs) 22, 22, . . . press from the lower direction thelower side side edge parts 3E, 3E of the lower side battery cells 3 dr,3 dl when the battery cell 3 is housed in the battery case 2 (refer toFIG. 13).

By the way, the projecting part 12 and the upper corner ribs 13 of theupper side case 10 and the lower corner rib part 22 and the small ribs21 of the lower side case 20 correspond to ┌side edge pressing part┘ inclaims.

A rectangular cutaway 23 is formed to open at a position that is thefront face and is biased to the right side from the central portion inthe left and right direction of the front face and at the front endportion of the undersurface continuous from the biased portion, and theabove-mentioned battery terminal 7 is slid from the upper direction andattached to the rectangular cutaway 23, with the front face of thebattery terminal attached to the rectangular cutaway 23 being made to beapproximately flush with the lower side case 20 (refer to FIG. 17).

A stepped difference is formed at the peripheral edge of an opening ofthe lower face of the upper side case 10 to face in the inner and lowerdirections, and a peripheral wall (hereinafter, referred to as ┌outerperipheral wall┘) 14 made thin of the upper side case is formed with ataper part 14 a being formed at the inside edge of the lower end edge ofthe outer peripheral wall (refer to FIG. 19).

The upper surface of the stepped difference is formed into an inclinedplane biased in the lower direction as the upper surface goes inside,and an inside portion having the inclined plane is formed into acircular projecting bar (hereinafter, referred to as ┌inside projectingbar┘)15, with the result that circular v groove 16 opening in the lowerdirection is formed between the inside projecting bar 15 and theabove-mentioned outer peripheral wall 14 (refer to FIG. 19).

In addition, the bottom (upper surface) 16 a of the v groove 16 isformed into a horizontal plane that is narrow in width with a taper part15 a being formed at the inside edge of the above-mentioned insideprojecting bar 15 (refer to FIG. 19).

A stepped difference facing in the outer and upper directions is formedat the upper peripheral edge of an opening of the lower side case 20,and a peripheral wall (hereinafter, referred to as ┌inner peripheralwall┘) 24 made thin of the inside of the lower side case 20 is formed,with the upper end of the inner peripheral wall 24 formed into a smallinclined plane (hereinafter, referred to as ┌outside inclined plane┘) 25on the outside thereof and a comparatively large inclined plane(hereinafter, referred to as ┌inside inclined plane┘) 26 on the insidethereof. The angle of the inside inclined plane relative to the verticaldirection is formed slightly smaller than that of the inclined plane ofthe inside projecting bar 15 that forms the v groove 16 of theabove-mentioned upper side case 10 (refer to FIG. 20). Meanwhile, theconcrete shapes of respective portions (numerical values) will bedescribed later on.

The battery cell 3 is shaped like a flat rectangular solid and comprisesa battery can 31 with one end thereof opening in the longitudinaldirection, a battery lid 32 to cover the opening of the battery cell 31,a battery device and the like, not shown in the figures, to be housed inthe battery can 31, and a positive pole terminal parts 33 is provided inthe battery lid 32 (refer to FIG. 6).

In addition, the positive pole terminals 33, 33 . . . provided in thebattery lids 32, 32, . . . of the respective battery cells 3, 3, . . .are provided at positions biased in one direction from the centralportion of the left and right direction, and two of the battery cells 3r, 3 l disposed left and right are combined with each other in a waythat the positive pole terminals 33 r, 33 l are oriented in a positionalrelationship to distance themselves from each other (refer to FIG. 6).

Further, since the two left and right battery cells 3 ur, 3 ul and 3 dr,3 dl connected in series of two up-and-down pairs of the battery cellsare such that the up and down battery cells are constituted the same, anexplanation will be given to one (up side) two left and right batterycells 3 ur, 3 ul, and a detailed explanation of the other (lower side)two left and right battery cells 3 dr, 3 dl will be omitted.

In examining the two left and right battery cells 3 ur, 3 ul from anelectrical view point, the right side battery cell 3 ur of the batterycells arranged in series is connected to the positive pole side, and theleft side battery cell 3 ul is connected to the negative pole side,respectively (refer to FIG. 6).

A positive pole side tab 34 with its tip extending rightward and beingfolded back forward is attached to a positive pole terminal part 33 urby spot welding (refer to FIGS. 4 and 6), with the tip portion that wasfolded back forward serves as a lead part 34 a to be soldered to theabove-mentioned substrate 6 (refer to FIG. 2).

An insulating sheet (cell side insulating sheet) 50 that isapproximately equivalent in size to the whole surface excluding left andright both side edges of the battery cells 3 ur, 3 ul is attached ontothe upper surface of the two battery cells 3 ur, 3 ul that are disposedleft and right, and a long aperture opening (hereinafter, referred to aslong-aperture opening) 51, from which a combined portion of the two leftand right battery cells is exposed is formed approximately in thecentral portion of the cell side insulating sheet 50. In addition, afolded part 52 folded downward for covering part of the battery lid 32is formed at the front edge of the insulating sheet 52 (refer to FIG.6). By the way, the portion between the left and right both side edgesof the cell side insulating sheet 50 and the left and right both sideedges of the battery cells 3 ur, 3 ul corresponds to ┌flank portion ofthe insulating sheet┘ in claim 3, and the above-mentioned long apertureopening 51 also corresponds to ┌flank portion of the insulating sheet┘in claim 3.

Then, in the right side battery cell 3 ur, there is provided anintermediate collection tab 36 that extends from a can bottom 35 ur ofthe battery cell 3 ur to the side of a battery lid 32 ur and creeps overthe upper side face of a battery can 31 ur through the above-mentionedcell side insulating sheet 50, the intermediate connection tab 36 beingdivided into two consisting of a can bottom side tab 36 a and a batterylid side tab 36 b in the front and back direction (refer to FIG. 6),with the end portion of the battery bottom side tab 36 a beingspot-welded to the can bottom 35 ur of the right side battery cell 3 ur(refer to FIG. 3). Further, the end portion of the battery lid side ofthe above-mentioned battery lid side tab 36 b, after extending in theleft direction, is folded downward to creep over a battery lid 32 ul,extending to a positive pole terminal part 33 ul of a left side batterycell 3 ul and is spot-welded to the positive pole terminal part 33 ul(refer to FIG. 4).

In addition, in the left side battery cell 3 ul, there is provided anegative side tab 37 that extends from a can bottom 35 ul to the side ofa battery lid 32 ul and creeps over the upper side face of a battery can31 ul through the above-mentioned insulating sheet 50, the negative poleside tab 37, as is the above-mentioned intermediate connection tab 36,being divided in two consisting of a can bottom side tab 37 a and a canlid side tab 36 b in the front and back direction (refer to FIG. 6),with the end portion of the above-mentioned can bottom side 37 aspot-welded to the can bottom 35 ul of the left side battery cell 3 ul(refer to FIG. 3). Further, the end portion of the battery lid side ofthe above-mentioned battery lid side tab 36 b has the front end thereoffolded downward and then folded forward on the front face side of thebattery lid 32 of the left side battery cell 3 ul, with the tip portionfolded forward serving as a lead part 37 c by being soldered to theabove-mentioned substrate 6 (refer to FIGS. 2 and 4).

As a result, since the above-mentioned cell side insulating sheet 50 isinterposed between the intermediate connection tab 36, the negative sidetab 37 and the battery cans 31 ur, 31 ul, insulation is establishedbetween the battery cans 31 ur, 31 ul and the intermediate connectiontab 36, the negative pole side tab 37, particularly between a batterylid side tab 36 b and 37 b of the respective tabs 36 and 37 (refer toFIG. 6).

PTC 38, 38 are interposed between the can bottom side tabs 36 a, 37 arespectively divided into two in the front and back direction of theabove-mentioned intermediate connection tab 36 and the negative poleside tab 37 and the battery lid side tab 36 b, 37 b, so that supply ofpower is shut off when the battery cells 3 ur, 3 ul become heated high(refer to FIG. 6).

Another insulating sheet (upper side insulating sheet) 53, approximatelythe same size of the above-mentioned cell side insulating sheet 50, isfurther attached onto the upper surface of the two left and rightbattery cells 3 ur, 3 ul over which these intermediate connection tab 36and the negative side tab 37 creep (refer to FIG. 6).

Specifically, the upper side insulating sheet 53 has rectangularopenings (hereinafter, referred to as ┌rectangular opening┘) 54, 54formed at the positions corresponding to the region where the bottomside tabs 36 a, 37 a and the battery lid side tabs 36 b, 37 b, of theabove-mentioned intermediate tab 36 and the negative side tab 37 areconnected with each other through the PTC 38, 38. Further, at theposition corresponding to the long-aperture opening 51, there is formeda long-aperture opening 55 that is the same size of the long-apertureopening 51 (refer to FIG. 6). By the way, the portions between the leftand right both side edges of the upper side insulating sheet 53 and theleft and right both side edges of the battery cells 3 ur, 3 ulcorrespond to ┌flank portion of the insulating sheet┘ in claims, and theabove-mentioned long-aperture opening 55 corresponds to ┌flank portionof the insulating sheet┘ in the scope of claims, and further, theabove-mentioned rectangular openings 54, 54 corresponds to ┌flankaperture in the insulating sheet┘ in claim 5.

Then, adhesive material is applied onto the surface of such upper sideinsulating sheet 53, which is attached onto the cell side insulatingsheet 50 on the above-mentioned battery cells 3 ur, 3 ul so as tosandwich the above-mentioned intermediate connection tab 36 and thenegative side tab 37.

As a result, the intermediate connection tab 36 and the negative poleside tab 37 are almost fixed on the side of the upper surface of the twobattery cells 3 ur, 3 ul by being disposed in a way that they do notmove easily, and the portions at which the can bottom side tabs 36 a, 37a and the battery lid side tabs 36 b, 37 b and the PTC 38, 38 areconnected, that is, the portions where thickness in the up and downdirection becomes thicker are exposed in the upper direction from therectangular openings 54, 54 of the upper side insulating sheet 53 (referto FIG. 4).

In the separator 4, a flat plate part 40 whose plane face is almost thesame as that of the two battery cells 3 r, 3 l disposed left and right,two substrate regulating pieces 41, 41 provided to project at the leftand right corner portions of the front end edge of the flat plate part40 to extend in the up and down direction thereof and battery cellsregulating pieces 42, 42 projected in the up and down direction at theback end edge of the above-mentioned flat plate part 40 so as tocorrespond to the can bottoms 35, 35, . . . of the respective batterycells 3, 3, . . . are integrally formed (refer to FIG. 9).

The substrate regulating pieces 41, 41 are ones for securing a space inthe front side within the battery case 2 so as to house theabove-mentioned substrate 6 when the separator 4 is housed in thebattery case (refer to FIGS. 17 and 18).

The two battery regulating pieces 42, 42 formed at the back end edge ofthe flat plate part 40 are ones for determining the positions in thefront and back direction of the two left and right battery cells 3 ur(dr), 3 ul (dl)(of upper side and lower side) with the can bottoms 35,35 . . . of the two battery cells coming in contact therewith (refer toFIGS. 17 and 18). Further, the portions projecting downward of thebattery cell regulating pieces 42, 42 have rectangular cutaways formedin the central portions thereof, with the result that the can bottomside tabs 36 a, 37 a of the lower side two battery cells 3 dr, 3 dl donot interfere with the battery cell regulating pieces 42, 42 (refer toFIG. 3).

On the upper surface of the flat plate part 40 of the separator 4, thereare an upper surface central flat projecting bar 43 in the centralportion thereof, extending in the front and back direction, uppersurface left and right flat projecting bars 44, 44 at the left and rightboth side edges of the projecting bar 43, extending in the front andback direction, all of them being integrally formed with separator 4,and flat projecting parts 43 a, 43 a, 44 a, 44 a, . . . further slightlyprojecting upward are formed at the front end and back end portions ofthe respective flat convex parts 43 a, 43 a, 44 a, 44 a (refer to FIG.9).

Meanwhile, the positions where the respective flat convex parts 43 a, 43a, 44 a, 44 a, . . . are formed are made to correspond to the referenceposition in thickness dimension of the battery cell 3.

Namely, since the battery can 31 of the battery cell 3 is usually formedby draw processing, it is difficult to accurately process the thicknessin the up and down direction of every position. Therefore, as for thethickness (dimension in the up and down direction) of the battery can31, of the peripheral edge thereof seen flatways, it is a commonpractice to choose several positions serving as reference dimensions andto mold the battery can 31 by increasing the accuracy of dimensions atthe reference positions.

As a result, these reference positions are accurately formed regionswith respect to the thickness of the battery cell 3, and pressing theregions by the inner face of the battery case 2 does not invite anemergence of dimensional errors of the both. Consequently, the batterycell 3 can be pressed without play when it is housed in the battery case2.

On the under surface of the flat plate part 40 of the separator 4, thereare an under surface central flat projecting bar 45 in the centralportion thereof, extending in the front and back direction, an undersurface left and right flat projecting bars 46, 46 at the left and rightboth side edges of the flat projecting bar 45, extending in the frontand back direction, all of them being integrally formed with theseparator 4, and further, flat convex parts 46 a, 46 a, . . . slightlyprojecting downward are formed at the front end and back end portions ofthe under surface left and right flat projecting bars 46, 46 (refer toFIG. 10). Meanwhile, such flat convex parts 46 a, 46 a, . . . are formedalso at the positions corresponding to the reference positions inthickness dimensions of the battery cell 3.

In addition, on the under surface of the flat plate part 40, there areformed flat concave parts (hereinafter, referred to as ┌under surfaceflat concave parts┘) 47, 47 long in the front and back direction (referto FIG. 10) between the above-mentioned under surface central flatprojecting bar 45 and each of the both left and right flat projectingbars 46, 46, and the under surface flat concave parts 47, 47 correspondto the portions where the can bottom side tabs 38, 38 and the batterylid side tabs 36 a, 37 a and the PTC 38, 38 are connected with eachother, that is, the ones where thickness in the up and down directionbecome thicker (refer to FIG. 13).

The two battery cells 3 r, 3 l disposed left and right as mentionedabove are attached onto the upper surface side and the lower face sideof the separator 4 that is formed in this manner.

Specifically, a double-faced adhesive sheet 60 with two rectangularapertures 60 a, 60 a formed therein, that is one size smaller than theplane form of the battery cell 3, is attached onto the upper surface ofthe separator 4, and the two battery cells 3 ul, 3 ur are placed thereonto eventually be attached onto the separator 4 (refer to FIG. 4).

At this time the respective battery cells 3 ur, 3 ul are placed on therespective flat convex parts 43 a, 43 a, 44 a, 44 a, . . . at the bothsides in the front and back direction of the above-mentioned uppersurface central flat projecting bar 43 and the upper surface left andright flat projecting bars 44, 44, that is, the back end side edge parts3E, 3E and the front biased left and both side edge parts 3E, 3E come incontact with the separator 4 through the above-mentioned double-facedadhesive sheet 60. Therefore, the under surfaces of the battery cells 3ur, 3 ul are in the state of having gaps with the separator 4 (refer toFIGS. 14 and 15). By the way, the above-mentioned double-faced adhesivesheet 60 is graphically not shown in FIGS. 14 through 18.

A double-faced adhesive sheet 61 that is similar to the double-facedadhesive sheet 60 attached onto the above-mentioned upper surfacethereof is attached onto the under surface of the separator 4, and thetwo battery cells 3 dr, 3 dl are positioned thereunder to eventually beattached to the separator 4 (refer to FIG. 4).

At this time the respective flat convex parts 46 a, 46 a, . . . at bothsides in the front and back direction of the above-mentioned undersurface central flat projecting bar 45 and the under surface left andright flat projecting bars 46, 46 come in contact with the battery cells3 dr, 3 dl, that is, the back end side edge parts 3E, 3E and the frontbiased left and right both side end edge parts 3E, 3E come in contactwith the separator 4. In addition, the portions where the can bottomside tabs 38 a, 37 a and the battery lid side tabs 36 b, 37 b and PTC38, 38 are connected with each other, that is, the ones where thethickness in the up and down direction thereof becomes thicker arepositioned within the above-mentioned under surface flat concave parts47, 47 without coming in contact with the separator 4, and are in thestate of having predetermined gaps (refer to FIGS. 14 and 15). By theway, the above-mentioned double-faced adhesive sheet 61 is notgraphically shown in FIGS. 14 through 18.

An IC chip 5 is mounted on the left side of the substrate 6 that isprovided in front of the four battery cells 3, 3, . . . disposed in thefront and back, and the left and right, directions, and the batteryterminal 7 is mounted on the lower portion at the right side thereofwith an insulating sheet (hereinafter, referred to as ┌substrate sideinsulating sheet┘) 70 interposed between the substrate 6 and the fourbattery cells 3, 3, . . . (refer to FIG. 5).

In the substrate 6, land apertures 6 a, 6 a, . . . are formed atpositions corresponding to lead portions 34 a, 34 a, 37 c, 37 c of thepositive pole side tabs 34, 34 and the negative pole side tabs 37, 37 inthe above-mentioned respective battery cells 3, 3, . . . . Further, cutlines 71, 71, . . . are formed at positions corresponding to the landapertures 6 a, 6 a, . . . of the substrate 6 in the substrate sideinsulating sheet 70 (refer to FIG. 5).

Then the substrate 6 is assembled to the respective battery cells insuch a way that first of all, the lead parts 34 a, 34 a, 37 c, 37 c ofthe respective positive side tabs 34, 34 and the negative pole side tabs37, 37 are passed through the respective cut lines 71, 71 of thesubstrate side insulating sheet 70. And after being passed through therespective land apertures 6 a, 6 a, . . . of the substrate 6, therespective lead parts 34 a, 34 a, 37 c, 37 c projecting from the landapertures 6 a, 6 a, . . . of the substrate 6 are soldered onto thesubstrate 6 (refer to FIG. 2).

Consequently, the left and right two battery cells 3 r, 3 l of the fourbattery cells 3, 3, . . . are connected in series, and the upper sideand lower side two pairs of the battery cells 3, 3, . . . are connectedin parallel (refer to FIG. 2).

By the way, a cutaway, not a cut line, is formed at a position in thesubstrate side insulating sheet 70 as corresponds to the lead part 37 cof the negative pole side tab 37 of the left upper side battery cell 3ul (refer to FIG. 5). This is because the upper side edge portion of thesubstrate side insulating sheet 70 is positioned at the reverse side ofthe folded part 52 of the upper side insulating sheet 53 and the leadpart 37 c of the negative pole side tab 37 of the left upper sidebattery cell 3 ul is positioned to creep over the front face of thefolded part 52.

Therefore, the four battery cells 3, 3, . . . to which the substrate 6is attached in this manner are housed in the battery case 2, and thebattery pack 1 is assembled in the following manner.

First the four battery cells 3, 3, . . . that are combined with eachother in the up and down, and left and right, directions are housed inthe lower side battery case 20 from the upper direction.

At this time the battery terminal 7 is slide-inserted in the rectangularcutaway 23 of the lower side case 20 from the upper direction (refer toFIG. 2). As the result the battery terminal 7 is positioned in the frontand back, and the left and right, directions with respect to the lowerside case 20.

In addition, the lower side two battery cells 3 dr, 3 dl of the housedfour battery cells 3, 3, . . . are placed on the small ribs 21, 21 andthe lower corner ribs 22, 22, . . . of the lower side case 20, that is,only the left and right both side edge parts 3E, 3E of the battery cells3 dr, 3 dl come in contact with the lower side case 20, leading to astate in which gaps emerge between the large portion of the undersurface of the battery cells 3 dr, 3 dl and the bottom of the lower case20.

Next the upper side case 10 and the lower side case 20 are joined witheach other so as to cover the battery cells 3, 3, . . . to combine theboth (refer to FIGS. 13 and 16).

First of all, the upper end edge of the inner peripheral edge 24 formedat the opening edge of the lower side case 20 is engaged with the insideof the v groove 16 formed at the outer peripheral edge of the upper sidecase 10 (refer to FIG. 21).

At this time, since the taper part 14 a is formed inside the outerperipheral wall of the upper case 10, and the outside inclined plane 25is formed outside the inner peripheral wall 14 of the lower side case20, although the upper side case 10 and the lower side case 20 areshifted in the front and back, and the left and right, directions intheir positional relationship, engagement of the v groove 16 with theupper end edge of the inner peripheral wall 24 can be performed withoutfail (refer to FIG. 21).

In this state the inner side face of the outer peripheral wall 14 of theupper case 10 and the outside face of the inner peripheral wall 24 comein contact with each other face to face in the way that the face of theupper side case 10 and that of the lower side case 20 are approximatelyflush with each other (refer to FIG. 21).

In addition, when the upper side case 10 is joined with the lower sidecase 20, since the opening edge at the right front side of the upperside case 10 is pressed from the upper direction, positioning in the upand down direction of the batter terminal 7 is performed in the way thatthe battery terminal 7 is held between the lower side case 20 and theupper side case 10 to be fixed to the inside of the batter case 2.

Next, ultrasonic welding is applied to the upper side case 10 and thelower side case 20, and the both are combined with each other (refer toFIGS. 23 and 24).

Specifically, the upper side case 10 and the lower side case 20 in thestate of being combined with each other are turned upside down andplaced on a receiving platform 81 of an ultrasonic welding device 80(refer to FIGS. 23 and 24).

In addition, specific forms (numerical values) of respective portions ofeach of the opening peripheral edges of the upper side case 10 and thelower side case 20 will be shown in FIGS. 19 and 20. These numericalvalues are one example from first to last, and the present invention isnot limited thereto.

The thickness of the upper side case is formed 1.0 mm, and that of theouter peripheral wall 0.45 mm. The height from the v groove bottom 16 aof the outer peripheral wall 14 is formed 0.7 mm, and the width of the vgroove bottom (horizontal plane) 16 a is formed 0.15 mm. The angle ofthe inclined plane forming the v groove 16 of the inside projecting bar15 is formed 42.0° relative to the vertical line, and the height fromthe v groove bottom 16 a of the inside projecting bar 15 is formed 0.3mm (refer to FIG. 19).

Further, the thickness of the lower side case 20 is formed 1.0 mm, andthat of the inner peripheral wall 24 of the lower side case 20 0.525 mm.The height of the inner peripheral wall is formed 1.2 mm, and that ofthe region where the outside inclined plane 25 is formed is 0.3 mm whilethat of the region where the inside inclined plane is formed is 0.665mm, and the angle of the inside inclined plane 26 relative to thevertical line 32.6° (refer to FIG. 20).

The above-mentioned receiving platform 81 has receiving jigs 82, 82 toapproximately surround the upper side case 10 from the front and back,and the left and right, four directions, with gaps of inasmuch as 0.1 mmformed in-between (refer to FIGS. 23 and 24).

Next, a welding hone 83 of the ultrasonic welding device 80 is made tocome in contact with the upper surface of the lower side case 20 that isturned upside down with appropriate contact pressure, and vibrations inpredetermined frequencies are added thereto (refer to FIG. 24).

As the result, the contact portions of the upper side case 10 and thelower side case 20, that is, the bottom 16 a of the v groove 16 of theupper side case 10 and the tip portion of the inner peripheral wall 24of the lower side case 20 are welded (refer to FIG. 22).

In the case of the upper side case 10 and the lower side case 20 in theabove-mentioned dimensions, such welding is to be terminated when theamount of welding becomes 0.25 mm, that is, at the position in which theheight in the welding direction is reduced by 0.25 mm (refer to FIG.22).

Since melted material, at the time of welding, of the upper side case 10and the lower side case 20 flows into gaps between the bottom 16 a ofthe v groove 16 of the upper side case 10 and the outside inclined plane25 of the inner peripheral wall 24 of the lower side case 20, a spacebetween the inclined plane of the v groove 16 and the inside inclinedplane 26 of the inner peripheral wall 24, and to the taper part 15 a ofthe inside projecting bar 15 of the upper case 10, superfluous weldingmaterial scarcely protrudes to the inner face side of the battery case 2(refer to FIG. 22).

Such welding is performed to the position where the upper end edge ofthe inner peripheral wall 24 of the lower side case 20 is melted by 0.25mm in the height dimension, and since the inside face of the outerperipheral wall 14 of the upper side case 10 and the outside face of theinner peripheral wall 24 are brought in slide-contact with each other,the stepped difference part 11 is not generated between the face of theupper side case 10 and that of the lower side case 20, which means boththe faces become approximately flush with each other, lending a goodappearance (refer to FIG. 22).

In addition, forming of a welding portion of 0.25 mm for the width ofthe upper side case 10 and the lower side case 20 is sufficient in termsof intensity, and in the case of welding of more than that amount,melted material protrudes, lending a bad appearance.

Therefore, in the state of the four battery cells 3, 3, . . . beinghoused in the battery case 2, the left and right both side edge parts3E, 3E of the respective battery cells 3, 3, 3, . . . become the stateof being held between the battery case 2 and the separator 4, with gapsresultantly formed between the upper surface and the battery case 2, andbetween the under surface of the respective battery cells 3, 3, . . .and the separator 4 (refer to FIGS. 14 and 15).

Specifically, since the under surface side left and right both side edgeparts 3E, 3E . . . of the upper side two battery cells 3 ur, 3 ul comein contact with the flat convex parts 43 a, 43 a, 44 a, 44 arespectively formed in the front and back both end portions of the threeflat projecting bars (upper surface central flat projecting bar 43 andupper surface left and right flat projecting bars 44, 44) formed on theupper surface side of the separator 4 through the double-faced adhesivesheet 60, predetermined gaps are formed between the under surfaces ofthese upper side two battery cells 3 ur, 3 ul and the separator 4, andfurther, predetermined gaps are formed between the upper surface ofthese upper side two battery cells 3 ur, 3 ul and the above-mentionedinner side face of the upper side case 10 as the upper surface left andright both side edge parts 3E, 3E, . . . come in direct contact with theprojecting part 12 provided to project approximately in the centralportion of the inner side face of the upper side case 10 and the uppercorner ribs 13 (refer to FIGS. 14 and 15).

The upper surface side left and right both side edge parts 3E, 3E, . . .of the lower side two battery cells 3 dr, 3 dl come in contact with theflat convex parts 46 a, 46 a, . . . through the double-faced adhesivesheet 60, that are formed at the both front and back end portionsrespectively formed in the under surface side central flat projectingbar 45 and the under surface side left and right flat projecting bars46, 46 on the under surface side of the separator 4, with predeterminedgaps being resultantly formed between the upper surface of these lowerside two battery cells 3 dr, 3 dl and the separator 4. Further, withboth the under surface side left and right side edges 3E, 3E thereofcoming directly in contact with the small ribs 21, 21 formedapproximately in the central portion of the lower inner side face andthe lower corner ribs 22, 22, predetermined gaps are formed between theunder surface of the lower side two battery cells 3 dr, 3 dl and thelower inner side face of the lower side case 20 (refer to FIG. 14, FIG.15).

Particularly, the gaps between the upper surfaces sides of therespective battery cells 3, 3, . . . and the battery case 2 or theseparator 4 are comparatively large, and in the gaps are positioned theabove-mentioned negative pole side tab 37 and the intermediateconnection tab 36. In spite of the negative pole side tab 37 and theintermediate connection tab 36 being positioned, further gaps can be hadtherebetween (refer to FIGS. 14 and 15).

Meanwhile, the contact between the respective side edge parts 3E, 3E, .. . of the above-mentioned battery cells 3, 3, . . . and the separator 4is performed through the double-faced adhesive sheets 60, 61 asmentioned above.

The distance between the tips of the upper corner ribs 13, 13, . . . andthose of the lower corner ribs 22, 22, . . . opposed to each otherwithin the battery case 2 assembled as mentioned above and thedimensions in the height direction of the four battery cells 3, 3, . . .combined with each other through the separator 4 are formed to be thesame or in the way that the height of the battery cells 3, 3, . . . isslightly larger. Consequently, in the state of the battery cells 3, 3, .. . being housed in the battery case 2, the respective double-facedadhesive sheets 60, 61 are slightly crushed so that the battery cells 3,3, . . . do not become wobbly in the battery case 2.

Further, since the respective side edge parts 3E, 3E, . . . of thebattery cells 3, 3, . . . are directly pressed by the projecting part 12of the upper side case 10, the upper corner ribs 13 (side edge pressingpart), the lower corner ribs 22 (side edge pressing part) and the smallribs 21 (side edge pressing part) of the lower side case 20, allprovided in the inner side face of the battery case 2, the state of thebattery cells 3, 3, . . . housed in the battery case 2 can be made freefrom play, so that the battery cells 3, 3, . . . can be stably held inthe battery case 2.

Then, when the battery pack 1 is charged, since the battery can 31 ofeach of the respective battery 3, 3, . . . is shaped like a flat squaresolid, the central portions of the upper surface and the under surfacethereof bulge out, but because of the above-mentioned gaps being formedbetween the respective battery cells 3 and the upper side case 10, thelower side case 20 or the separator 4, the amount of bulging of thebattery cell 3 can be absorbed within the gaps, so that the whole of thebattery case 2 never swells nor deforms (refer to FIGS. 16 and 18). Inthe meantime, the battery cells 3, 3, . . . shown in FIG. 16 and FIG. 18by a continuous line indicate bulging states of the battery cell 3, 3, .. . and the battery cells 3, 3, . . . shown by a two-dot line indicatethe states before bulging thereof.

Further, in the embodiments mentioned above, explanations have beengiven of the case in which by joining the upper side battery case 10with the lower side battery case 20 in a way to cover the battery cells3, 3, . . . , combination of them are performed by ultrasonic weldingwith the opening peripheral edges of the both in the state of beingjoined with other. However, the present invention is not limited theretoas the two may be combined with each other by using adhesive material.

In addition to this, the specific forms and structures of the respectiveportions shown in the above-mentioned embodiments are only one examplefor implementing the present invention, and therefore, the technologicalscope of the present invention should not be limitedly construed.

As is apparent from the descriptions made thus far, a battery pack ofthe present invention is a battery pack characterized by connecting inseries and housing a plurality of square pole-like battery cells in abattery case, the battery case comprising a respectively box-like upperside case and lower side case joined with each other, the plurality ofthe battery cells having battery lids respectively positioned on thefront side thereof and lining up in the left and right direction to behoused in the above-mentioned battery case; wherein there are provided anegative pole side tab extending to the battery lid side connected tothe bottom of a battery can of a battery cell, an intermediateconnection tab connecting a positive pole terminal part of the negativepole side battery cell to the bottom of a battery can of adjacentanother battery cell and a positive pole side tab connected to apositive pole side terminal part of said another battery cell, theabove-mentioned negative pole side tab and the intermediate connectiontab being provided to creep over the side of the battery can of each ofthe respective battery cells by being respectively divided into two canbottom side tab and battery lid side tab, with PTC (positive temperaturecoefficient) interposed between these can bottom side tab and batterylid side tab; and further, a cell side insulating sheet is providedbetween the respective negative pole side tab, the intermediateconnection tab and the side of each of the respective battery cans; andside edge pressing parts respectively are provided on the inner face ofthe upper side case and on the inner face of the lower side case topress the side edge portions extending in the front and back directionof the respective battery cells when the upper side case and the lowerside case are combined with each other.

Therefore, according to a battery pack of the present invention, sincethe battery pack has provided in a battery case side edge pressing partsto press the side edge portions extending in the front and backdirection of battery cells, the battery cells can be held without playwhen the battery cells are housed in the battery case, and predeterminedgaps are formed between the central portion of the battery cells housedin the battery case and a separator; and when the battery cells swell ata time of the battery pack being charged and the central portions of theupper surface and the under surface bulge out, since the above-mentionedgaps can absorb the amount of bulging, it is possible to prevent thewhole of the battery case from swelling and deforming.

According to the present invention, the above-mentioned negative poleside tab and intermediate connection tab are held between a cell sideinsulating sheet and another upper side insulating sheet attached to theupper side thereof, the negative pole side tab and intermediateconnection tab are approximately fixed onto the upper surface side anddisposed in such a way that they do not move easily. Consequently, evenin the case where the battery case is accidentally dropped, there are nomovements of the negative pole side tab and intermediate connection tab,thereby preventing the trouble in which they come in contact with abattery can.

According to the present invention, since a flank portion is provided inthe above-mentioned cell side insulating sheet so that a side edgepressing part directly contacts with battery cells, it is possible tostably hold the battery cells.

According to the present invention, flank apertures are provided in theregions of the above-mentioned upper side insulating sheet, thatcorrespond to the above-mentioned PTC, the amount of thickness of a canbottom side tab, PTC, a battery and lid side tab that are superposed upone on top another can be absorbed, if only a little, therebycontributing to thinning of the thickness of a battery pack.

1. A battery pack in which a plurality of square pole-like battery cellsare connected in series and housed in a battery case, characterized inthat: the battery case is comprised of a respective box-like upper sidecase and lower side case combined with each other, the plurality of thebattery cells each have a battery lid respectively positioned on thefront side thereof and are lined up in the left and right direction tobe housed in said battery case, a negative pole side tab extending tothe battery lid side connected to the battery can bottom of a batterycell, an intermediate connection tab connecting a positive pole terminalpart of the battery cell to the battery can bottom of adjacent anotherbattery cell, and a positive pole side tab connected to a positive poleside terminal part of said another battery cell are provided, saidnegative pole side tab and intermediate connection tab are provided tocreep over the sides of the battery cans of the respective batterycells, said negative pole side tab and intermediate connection tab arerespectively divided into two of a can bottom side tab and a battery lidside tab with PTC (positive temperature coefficient) interposed betweenthese can bottom side tab and battery lid side tab, an insulating sheet(hereinafter, referred to as ┌cell side insulating sheet┘) is providedbetween the respective negative pole side tab, intermediate connectiontab and the sides of the respective battery cans; and side edge pressingparts are respectively provided on the inner face of the upper side caseand on the inner face of the lower side case to press the side edgeportions extending in the front and back direction of the respectivebattery cells when the upper side case and the lower side case arecombined with each other.
 2. A battery pack according to claim 1,wherein said negative pole side tab and intermediate connection tab areheld between the cell side insulating sheet and another insulating sheet(hereinafter, referred to as ┌upper side insulating sheet┘) attachedonto the upper side thereof.
 3. A battery pack according to claim 1,wherein a flank portion is provided in said cell side insulating sheetfor the side edge pressing parts to directly come in contact with thebattery cells.
 4. A battery pack according to claim 2, wherein a flankportion is provided in said upper side insulating sheet for the sideedge pressing parts to directly come in contact with the battery cells.5. A battery pack according to claim 1, wherein flank apertures areprovided in regions corresponding to said PTC of said upper sideinsulating sheet.